Volumetric capnography pre- and post-surfactant during initial resuscitation of premature infants.

Background: Volumetric capnography allows for continuous monitoring of expired tidal volume and carbon dioxide. The slope of the alveolar plateau of the capnogram (S _III ) could provide information regarding ventilation homogeneity. We aimed to assess the feasibility of measuring S _III during newborn resuscitation and determine if S _III decreased after surfactant indicating ventilation inhomogeneity improvement.
Methods: Respiratory function traces of preterm infants resuscitated at birth were analysed. Ten capnograms were constructed for each infant: five pre- and post-surfactant. If a plateau was present S _III was calculated by regression analysis.
Results: Thirty-six infants were included, median gestational age of 28.7 weeks and birth weight of 1055 g. Average time between pre- and post-surfactant was 3.2 min. Three hundred and sixty capnograms (180 pre and post) were evaluated. There was adequate slope in 134 (74.4%) capnograms pre and in 100 (55.6%) capnograms post-surfactant (p = 0.004). Normalised for tidal volume S _III pre-surfactant was 18.89 mmHg and post-surfactant was 24.86 mmHg (p = 0.006). An increase in S _III produced an up-slanting appearance to the plateau indicating regional obstruction.
Conclusion: It was feasible to evaluate the alveolar plateau pre-surfactant in preterm infants. Ventilation inhomogeneity increased post-surfactant likely due to airway obstruction caused by liquid surfactant present in the airways.
Impact: Volumetric capnography can be used to assess homogeneity of ventilation by S _III analysis. Ventilation inhomogeneity increased immediately post-surfactant administration during the resuscitation of preterm infants, producing a characteristic up-slanting appearance to the alveolar plateau. The best determinant of alveolar plateau presence in preterm infants was the expired tidal volume.
(© 2021. The Author(s).)